Process for oxidizing a 1,1-bis-(alkyl-phenyl)alkane



United States Patent 3,424,739 PROCESS FOR ()XIDIZING A 1,1-BIS- (ALKYL-PHENYL)ALKANE Johann G. D. Schulz, Arthur C. Whitaker, and Paolo Winteler, Pittsburgh, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., 21 corporation of Delaware N0 Drawing. Filed Mar. 5, 1964, Ser. No. 349,767 US. Cl. 260-517 18 Claims Int. Cl. C07c 65/20 This invention relates to a process for oxidizing a 1,1- bis-(alkylphenyl) alkane with molecular oxygen.

The 1,1-bis-(alkylphenyl) alkane that is subjected to oxidation with molecular oxygen is one wherein said alkyl has from one to 16 carbon atoms, preferably from one to eight carbon atoms, and said alkane has from two to 16 carbon atoms, preferably from two to eight carbon atoms. Specific examples of 1,l-bis-(alkylphenyl) alkanes that can be employed are 1,1-bis-(p-tolyl) ethane, 1,1-bis-(ptolyl) propane, l,l-bis-(ptolyl) butane, 1,1-bis-(p-tolyl) hexane, 1,1-bis-(p-tolyl) octane, 1,1-bis-(p-tolyl) decane, 1,1-bis-(p-tolyl) dodecane, 1,1-bis-(p-tolyl) tetradecane, 1,1-bis-(p tolyl) hexadecane, 1,1 bis (4 ethylphenyl) ethane, 1,1-bis-(4-octylphenyl) pentane, 1,1-bis-(4-decylphenyl) octane, l,l-bis-(4-hexadecylphenyl) hexadecane, 1,l-bis-(3,4-dimethylphenyl) ethane, l,1-bis(3,4-dimethylphenyl) propane, 1,l-bis-(3,4-dimethylphenyl) butane, 1,l-bis-(3,4-dimethylphenyl) hexane, l,1-bis-(3,4-dimethylphenyl) octane, 1,1-bis-(3,4-dimethylphenyl) decane, 1, 1-bis(3,4-dimethylphenyl) dodecane, 1,1-bis-(3,4-dimethylphenyl) tetradecane, 1,l-bis-(3,4-dimethylphenyl) hexadecane, l,l-bis-(3,4-diethylphenyl) ethane, l,l-bis-(3,4- octylphenyl) pentane, 1,1-bis-(3,4-decylphenyl) octane, l, l-bis(3,4-hexadecylphenyl) hexadecane, 1,l-bis-(2,2 -dibrorno, 3,4,3,4-tetramethylphenyl) ethane, l-(3-methyl, 4-ethylphenyl), 1-(2-nitro, 3,4-diethylphenyl) ethane, 1,1-bis-(3,4,3,4-tetramethyl, 5 aminophenyl) ethane, 1 (3,4 diethylphenyl), 1 (3',4 diisopropyl phenyl) ethane, 1-(2-methyl-4, isopropyl-phenyl), l-(4-methyl-2- nitrophenyl) ethane, 1,1-bis-(3-ethyl, 4-butylphenyl) isobutane, 1 (4 propylphenyl), l-(Z-ethylphenyl) octane, 1,1-bis-(2,4-diisopropylphenyl) hexadecane, 1,1 bis (2- ethyl, 4-butylphenyl) isobutane, etc.

The oxidation of a bis-(alkylphenyl) methane with molecular oxygen in the presence of catalytic amounts of a catalyst, such as cobalt acetate, can proceed without undue difiiculty to the corresponding benzophenone carboxylic acid. Initially the oxidation converts the bis-(alkylphenyl) methane to the corresponding hydroperoxide. The hydroperoxide portion is unstable and cleavage occurs between the adjacent oxygen atoms, thereby producing a diphenylmethoxy radical. Since the hydrogen attached to the bridge carbon has a greater migration aptitude than either of the phenyl groups attached to said bridge carbon, said hydrogen will preferentially split off. The alkyl substituents on the ring will also be oxidized to obtain carboxylic acid functions and as a result of these actions a benzophenone carboxylic acid is formed and water is obtained as a by-product.

One the other hand, when a 1,1-bis- (alkylphenyl) alkane, such as defined, is oxidized with molecular oxygen to obtain a benzophenone carboxylic acid difficulty arises. As with a bis-(alkylphenyl) methane, oxidation with molecular oxygen results in the formation of the corresponding hydroperoxide and, since the latter is relatively unstable, cleavage occurs, as before, between the adjacent oxygen atoms thereon. However, the migration aptitude of the phenyl groups attached to the bridge carbon is greater than the migration aptitude of the alkyl substituent attached to said bridge carbon and therefore there is a tendency for one of the phenyl groups to leave and form a phenol and to obtain an acetophenone as an additional product.

We have found, however, that we can oxidize a 1,1-bis- (alkylphenyl) alkane to promote the formation of a benzophenone carboxylic acid and inhibit the formation of a phenol and an acetophenone by oxidizing the same at moderate temperatures with molecular oxygen in the presence of a catalyst in an amount sufficient not only to form the corresponding hydroperoxide but also sufiicient selectively to split off the alkyl substituent attached to the bridge carbon but not either of the phenyl substituents attached thereto. In the case wherein a bis-(alkylphenyl) methane is oxidized with molecular oxygen only sufllcient amounts of catalyst need be present to obtain the desired hydroperoxide, since heat alone will selectively separate the hydrogen from the bridge carbon of the diphenylmethoxy radical. As noted above, this will not have a tendency to occur when a 1,1-bis-(alkylphenyl) alkane is oxidized with molecular oxygen. We have found that by operating at mild temperatures and by employing a catalyst in an amount in excess of that catalytically required to obtain the desired hydroperoxide we can inhibit the undesired tendency referred to above and also obtain the desired cleavage to thereby produce the desired benzophenone carboxylic acid.

The reaction defined herein can be carried out by bringing together the 1,1-bis-(alkylphenyl) alkane defined above and molecular oxygen such as air, preferably by passing the latter therethrough, at moderate temperatures and pressures in the presence of a selected amount of catalyst. The total amount of oxygen required per total mol of charge to be oxidized is at least about one, but preferably about eight to about 16 mols. The temperature of the reaction can be as low as about 25 C., but in order to obtain a reasonable reaction rate we prefer to employ a temperature of at least about 50 C. Temperatures as high as about 110 C. can be employed, but in order to inhibit the formation of undesirable by-products we prefer to employ a temperature no higher than about C. Increasing the pressure on the reaction system increases the solubility of the molecular oxygen therein and would thereby normally increase the rate of reaction, but at the same time the increased pressure inhibits the formation of the desired hydroperoxide and therefore in effect reduces the amount of desired product. For this reason we prefer to operate the process at atmospheric pressure, although pressures as high as about 500 pounds per square inch gauge can be employed.

The length of the reaction period is dependent upon the nature of the product desired. As the hydroperoxide defined decomposes, the following desired compounds are formed: a 1,1-bis-(alkylphenyl) alkylene, a 1,1-bis-(alkylphenyl) alkylcarbinol, an alkylbenzophenone and an alkylbenzophenone mono carboxylic acid. A small amount of the following undesired compounds are also formed: phenols and acetophenones. The first three compounds defined in the list of desired compounds are precursors to the alkylbenzophenone mono carboxylic acid, and therefore with increased reaction time more of the desired benzophenone mono carboxylic acid is obtained, until continued oxidation results in a large conversion of the charge to benzophenone mono carboxylic acid and/or to a benzophenone carboxylic acid. Thus a reaction time of at least about 30 minutes, but preferably of about five to about 24 hours, is suflicient for the stated purposes.

As noted the amount of catalyst needed is the amount catalytically required to obtain the desired hydroperoxide and an additional amount sufiicient selectively to obtain the desired benzophenone, rather than the phenol and/or acetophenone, and to convert at least a portion of the alkyl substituents on the rings to the carboxylic acid function. We have found that these conditions are met when the amount of catalyst in the reaction system is from about 0.02 to about 10, preferably from about one to about five percent by weight relative to the 1,1-bis-(alkylphenyl) alkane charge. Best results are obtained when about three percent by weight of catalyst is employed. As catalysts for the process we prefer to employ a salt of an organic acid and a transition metal soluble in the reaction mixture. By organic acid we mean to include straight chain and cyclic organic acids having from six to 20 carbon atoms in the molecule. Examples of such acids are hexanoic acid, octanoic acid, stearic acid, naphthenic acids, etc. Examples of such metals are iron, cobalt, nickel, manganese, chromium, vanadium, molybdenum, etc. Examples of catalysts which can be employed include ferrous caprylate, cobaltous caprylate, cobaltous naphthenate, nickelous naphthenate, manganese caprylate, manganese naphthenate, chromous stearate, chromous hexanoate, vanadium naphthenate, molybdenum caprylate, molybdenum stearate, etc.

The work-up of the product thus obtained depends upon the nature thereof and the type of ultimate product desired. In the event only a portion of the product has been converted to a benzophenone carboxylic acid and it is desired not to proceed further with air oxidation, and yet still convert the precursors thereof to the desired benzophenone carboxylic acid, the entire air oxidation product can be further oxidized with nitric acid. This can be done, for example, by oxidizing the same with nitric acid having a concentration of from about five to about 70 percent, with the molar ratio of the nitric acid to the compound to be oxidized being from about 8.0 to about 17.0. The reaction temperature can be from about 110 to about 350 C., the reaction pressure from about atmospheric to about 500 pounds per square inch gauge and the reaction time from about one minute to about 48 hours.

In the event only a portion of the charge has been converted to a benzophenone carboxylic acid, and not all of the alkyl substituents thereon have been converted to carboxylic acid groups, and it is desired to oxidize only the same further to the extent that all of the alkyl groups thereon are so oxidized, the partially oxidized benzophenone carboxylic acid can be separated from the air-oxidized product and then subjected to oxidation with nitric acid in the manner described above. This separation can be effected by adding to the reaction mixture from about to about 50 percent by weight of benzene and sufiicient alkali, such as sodium hydroxide, to react with the benzophenone carboxylic acids and small amounts of cleavage products of phenolic nature present therein, such as alkyl phenols. An organic phase containbenzophenone and an aqueous alkaline phase containing the partially and/or fully oxidized benzophenone carboxylic acid and said cleavage products of phenolic nature are thus obtained.

The two phases so obtained are separated from each other, and the alkaline phase is treated with at least the stoichiometric amounts of an inorganic acid such as hydrochloric acid, at a temperature of about 10 to about C. to thereby precipitate the phenolic products and the benzophenone carboxylic acid. The precipitate is separated from the solution and treated with an aqueous solution of sodium bicarbonate. While the phenols will not be solubilized thereby, the alkaline metal salt of the benzophenone carboxylic acid will be solubilized. After separation of the phenolic products therefrom the solution can be treated with an inorganic acid to precipitate the benzophenone carboxylic acid. Heating the product will drive liquid therefrom, leaving behind substantially pure benzophenone carboxylic acid. In the event all of the alkyl substituents on the benzophenone carboxylic acid have been converted to carboxylic acid functions, no further work is desired. In the event some alkyl substituents still remain, and it is desired to convert the same to carboxylic acid functions, the benzophenone carboxylic acid containing alkyl substituents can be subjected to nitric acid oxidation as described.

The organic layer described above after removal of benzene therefrom by evaporation and upon standing at a temperature of about 0 to about 35 C. will result in the precipitation therein of the alkylbenzophenone, and the separation of the latter therefrom can be effected by filtration. The remainder of the organic layer can be diluted with an alcohol, such as methyl alcohol, and on cooling to a temperature of about 50 to about '10 C., removal of the 1,1-bis-(alkylphenyl) alkylene as a solid precipitate results. The residual organic layer can then be extracted with glycol which results in the removal therefrom of the 1,1-bis-(alkylphenyl) alkylcarbinol. The remainder is 1,1-bis-(alkylphenyl) alkane which is then recovered.

The invention can better be described by reference to the following. In each of the runs tabulated below oxygen was bubbled at atmospheric pressure through 510 grams of the defined 1,1-bis-(alkylphenyl) alkane and catalyst at a rate of 0.01 gram of oxygen per gram of charge per hour while the mixture was being stirred. In each run 1.4 percent by weight of methyl ethyl ketone, based on the charge, was added thereto as a promoter. In each of Tables I, II, III and IV 3.33 percent by weight of cobaltous caprylate, based on the charge, was employed. In Tables I, II, III, IV and V the charge was dixylylethane. Table I illustrates the effect of reaction time at a temperature of C.

TAB LE I Percent Weight percent Percent Percent efiiciency to Percent Run No. Time, of charge efficiency to efficiency to benzophenone etficiency to hours converted alcohol and alk mono by-products olefin benzophenone carboxylic acid ing benzene, unreacted charge, 1,1-bis-(alkylphenyl) alkylene, 1,1-bis-(alkylphenyl) alkylcarbinol and alkyl- In Table II below the effect of reaction time at 95 is illustrated.

TABLE II Percent Weight percent Percent Percent etficieney to Percent Run No. Time, of charge efiieieney to efiicieucy to benzophenone elficiency to hours converted alcohol and alkylmono by-products olefin benzophenone carboxylic acid The effect of temperature over a reaction period of 16 hours is illustrated below in Table III.

methyl benzophenone-4'-monocarboxylic acid, 4-methylphenol and 4-methylacetophenone.

TABLE III Percent Percent Percent Run Temp., Weight percent eflicieney efficiency efiiciency to Percent No. C. of charge to alcohol to alkylbenzophenone efficiency converted and olefin benzophenone mono carcllaoxylic to by-products aci The efiect of temperature over a reaction period of seven hours is illustrated below in Table IV.

In Tables I and II it can be seen that as reaction time increases the conversion of charge to acids and the de- TABLE IV Percent Percent Percent Run Temp., Weight percent efliciency efficiency efficiency to Percent N 0. C. of charge to alcohol to alkylbenzophenone efficiency converted and olefin benzophenone mono caraoxylic to byproducts The effect of catalyst concentration on the reaction at a temperature of 65 C. over a period of seven hours is illustrated below in Table V.

sired precursors thereto also increases. However, at the same level of reaction time greater conversion. with as TABLE V Percent Weight Percent Percent Percent Percent y percent of eificiency to efficiency to efficiency to efiiciency to Run No. weight of charge alcohol and alkylbenzophenone by-products catalyst converted olefin benzophenone mono caigooxylic That inabove can be made to work in this context is apparent from an inspection of the data in Table VI below. The salts employed were in the form of caprylates and 3.33 percent by weight, based on the charge, was employed. The temperature was 65 C. and the reaction time seven hours.

other catalysts within the definition set forth heregood or better selectivity to the desired acids and precursors thereto, occurs at the lower temperature level. This is further emphasized in Tables III and IV wherein it is seen that at the very high temperatures conversion drops oif markedly and selectivity to the desired compounds is greatly reduced. At the same time formation of undesired by-products is greatly increased.

TABLE VI Percent Percent Percent Weight percent efficiency efficiency efficiency to Percent Run No. Cation of charge to alcohol to alkyl benzophenone efficiency converted and olefin benzophenone mono cargoxylic to by-products 17 Co 44 .70 58 .60 12.22 26.62 2.52 18 Mn" 42 .77 34 .80 17 .09 42 .05 6 .07 19 Fe++ 14 .68 43 .13 20 .95 24 .02 5 .87

That the entire air oxidation product can be treated with nitric acid to obtain additional amounts of benzophenone carboxylic acids is seen from the following.

EXAMPLE I 191.0 grains of dixylylethane, 6.3 grams of cobaltous caprylate (3.33 weight percent) and 2.7 grams of methyl TABLE VII Percent Percent Percent Weight percent eiliciency efficiency efliciency to Percent Run No. Cation of charge to alcohol to elkyl benzophenone efliciency converted and olefin benzophenone mono cargoxyhc to lay-products aci DXE 44 .7 58.60 12.22 26.62 2.52 DTE 34 .4 52 .01 14 .63 26 .31 7 .01

In the tables above wherein the charge employed was dixylylethane the alcohol was dixylyl methyl carbinol, the olefin was 1,1-diXylyl ethylene, the alkylbenzophenone was tetramethyl benzophenone, the benzophenone mono carboxylic acid was trimethyl benzophenone mono carboxylic acid and the by-products were xylenol and dirnethyl acetophenone. The respective compounds wherein ditolylethane was employed as charge were ditolyl methyl ethyl ketone (1.41 weight percent) were contacted with molecular oxygen at the rate of 100 cc. of oxygen per minute over a period of seven hours at a temperature ranging between and C. at atmospheric pressure. The methyl ethyl ketone was evaporated during the reaction, and there was obtained 212.0 grams of an oxidation mixture. 67.0 grams of this mixture was treated in a one-liter stirred autoclave with 538.0 grams of 30 percarbinol, 1,1-ditolyl ethylene, dimethyl benzophenone, 4- 75 cent nitric acid at C. and 200 pounds per Square inch gauge for 2.5 hours. There was found 40.2 grams of 3,4,3,4'-benzophenone tetIacarboxylic acid.

That only the alkyl benzophenone mono carboxylic acid in the air oxidized reaction mixture can be treated with. nitric acid for the defined purpose can be seen from the following.

EXAMPLE II 191.0 grams of dixylylethane, 12.6 grams of cobaltous caprylate and 5.7 grams of methyl ethyl ketone were contacted with molecular oxygen at the rate of 100 cc. of oxygen per minute over a period of seven hours at a temperature ranging between 90 and 95 C. at atmospheric pressure. By alkaline treatment of the reaction mixture obtained there was recovered trimethyl benzophenone mono carboxylic acid. 67.0 grams of the latter acid was reacted in a one-liter stirred autoclave with 538.0 grams of 30 percent nitric acid at 170 C. and 200 pounds per square inch gauge for two hours. There was found 62.0 grams of 3,4,3',4-benzophenone tetracarboxylic acid.

That only the alkylbenzophenone in the air oxidized reaction mixture can be treated with nitric acid can be seen from the following.

EXAMPLE III 510.0 grams of dixylylethane, 17.0 grams of cobaltous caprylate and 7.2 grams of methyl ethyl ketone were contacted with molecular oxygen at the rate of 100 cc. of oxygen per minute over a period of 16 hours at a temperature ranging between 60 and 65 C. at atmospheric pressure. The reaction product was treated with an aqueous alkaline solution and subsequently extracted with benzene. Two phases, an alkaline soluble phase and a benzene soluble phase, were obtained. From the latter after evaporation of the solvent 3,4,3',4'-tetramethyl benzophenone was collected. 59.3 grams of this compound was reacted with 725 grams of 30 percent nitric acid in a one-liter stirred autoclave at 150 to 170 C. and 200 pounds per square inch gauge for 2.5 hours. 72.5 grams of 3,4,3,4'-benzophenone tetracarboxylic acid and grams of a mixture of trimellitic and other overoxidized products were obtained.

Obviously, many modifications and variations of the invention, as hereinabove set forth, can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for oxidizing a 1,1-bis-(alkylphenyl) alkane wherein said alkane has at least two carbon atoms which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about 0.10 to about percent by weight of a transition metal salt of a carboxylic acid to obtain a mixture containing a benzophenone carboxylic acid.

2. A process for oxidizing a 1,1-bis-(alkylphenyl) alkane wherein said alkane has at least two carbon atoms which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about 0.10 to about 10 percent by weight of a cobalt salt of a carboxylic acid to obtain a mixture containing a benzophenone carboxylic acid.

3. A process for oxidizing a 1,1-bis-(alkylphenyl) alkane wherein said alkane has at least two carbon atoms which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about 0.10 to about 10 percent by weight of a manganese salt of a carboxylic acid to obtain a mixture containing a benzophenone carboxylic acid.

4. A process for oxidizing a 1,1-bis-(alkylphenyl) alkane wherein said alkane has at least two carbon atoms which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C.

in the presence of about 0.10 to about 10 percent by weight of an iron salt of a carboxylic acid to obtain a mixture containing a benzophenone carboxylic acid.

5. A process for oxidizing a 1,1-bis-(alkylphenyl) alkane wherein said alkane has at least two carbon atoms which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about C. in the presence of about 0.10 to about 10 percent by weight of cobalt caprylate to obtain a mixture containing a benzophenone carboxylic acid.

6. A process for oxidizing a 1,1-bis-(alkylphenyl) alkane wherein said alkane has at least two carbon atoms which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about 0.10 to about 10 percent by weight of manganese caprylate to obtain a mixture containing a benzophenone carboxylic acid.

7. A process for oxidizing a 1,1-bis-(alkylphenyl) alkane wherein said alkane has at least two carbon atoms which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about 0.10 to about 10 percent by weight of ferrous caprylate to obtain a mixture containing a benzophenone carboxylic acid.

8. A process for oxidizing ditolylethane which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about one to about 10 percent by weight of a transition metal salt of a carboxylic acid to obtain a mixture containing a benzophenone carboxylic acid.

9. A process for oxidizing ditolylethane which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about one to about 10 percent by weight of cobalt caprylate to obtain a mixture containing a benzophenone carboxylic acid.

10. A process for oxidizing ditolylethane which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about one to about 10 percent by weight of manganese caprylate to obtain a mixture containing a benzophenone carboxylic acid.

11. A process for oxidizing ditolylethane which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the pres ence of about one to about 10 percent by weight of ferrous caprylate to obtain a mixture containing a benzophenone carboxylic acid.

12. A process for oxidizing dixylylethane which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about one to about 10 percent by weight a transition metal salt of a carboxylic acid to obtain a mixture containing a benzophenone carboxylic acid.

13. A process for oxidizing dixylylethane which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about one to about 10 percent by weight of cobalt caprylate to obtain a mixture containing a benzophenone carboxylic acid.

14. A process for oxidizing dixylylethane which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about one to about 10 percent by weight of manganese caprylate to obtain a mixture containing a benzophenone carboxylic acid.

15. A process for oxidizing dixylylethane which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about one to about 10 percent by weight of felrous caprylate to obtain a mixture containing a benzophenone carboxylic acid.

16. A process for oxidizing a 1,1-bis-(alkylphenyl) alkane wherein said alkane has at least two carbon atoms which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about one to about 10 percent by weight of a transition metal salt of a carboxylic acid to obtain a mixture containing a benzophenone cauboxylic acid and thereafter oxidizing said mixture with nitric acid.

17. A process for oxidizing ditolylethane which comprises oxidizing the sarne with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about one to about 10 percent by weight a transition metal salt of a carboxylic acid to obtain a mixture containing a benzophenone carboxylic acid and thereafter oxidizing said mixture with nitric acid.

18. A process for oxidizing dixylylethane which comprises oxidizing the same with molecular oxygen at a temperature of about 25 to about 110 C. in the presence of about one to about 10 percent by weight of a transition metal salt of a carboxylic acid to obtain a mixture containing a benzophenone carboxylic acid and thereafter oxidizing said mixture with nitric acid.

References Cited UNITED STATES PATENTS 3,075,007 1/1963 McCracken et a1. 260--517 FOREIGN PATENTS 533,179 3/1958 Belgium.

LORRAINE A. WEINBERGER, Primary Examiner.

MELVIN G. BERGER, Assistant Examiner.

US. Cl. X-R. 

1. A PROCESS FOR OXIDIZING A 1,1-BIS(ALKYLPHENYL) ALKANE WHEREIN SAID ALKANE HAS AT LEAST TWO CARBON ATOMS WHICH COMPRISES OXIDIZING THE SAME WITH MOLECULAR OXYGEN AT A TEMPERATURE OF ABOUT 25* TO ABOUT 110*C. IN THE PRESENCE OF ABOUT 0.10 TO ABOUT 10 PERCENT BY WEIGHT OF A TRANSITION METAL SALT OF A CARBOXYLIC ACID TO OBTAIN A MIXTURE CONTAINING A BENZOPHENONE CARBOXYLIC ACID. 